1. Field of the Invention
The invention relates to a switch for actuating a gear on a bicycle.
2. Description of the Related Art
A known switch for actuating a gear on a bicycle is disclosed by German Patent Application No. 198 35 118.6, published as earlier priority No. 199 18 520.4. This switch comprises a housing for fastening the switch on the bicycle and a grip element for actuating the switch. The switch also includes a rotary element and a cable-storage device, in particular a winding drum for winding up a cable for actuating the gear. The rotary element is connected to the winding drum and has at least one detent pawl which engages in a latching toothing formation in the housing. The advantage here is that a carry-along element on the grip element carries along the rotary element directly in a tensioning direction and the movement of the rotary element in the opposite rotational direction, namely in the release direction of rotation, is brought about by the detent pawl being released. In the release direction of rotation, a spring element pretensions the rotary element, with the result that the switching operation takes place in an accelerated manner. The spring element comprises a spiral spring which is positioned under pretensioning in a groove in the rotary element and is actuated by a carry-along element on the grip element.
It is an object of the present invention to provide a switch which has improved functioning and comprises only a small number of parts, the intention being to reduce the production costs in relation to the known switch configurations.
The switch according to the present invention includes a housing, a grip element, a rotary element, and a cable drum. The housing has a pawl for retaining the individual gear stages relative to the housing. The switch according to the present invention further includes an improved spiral-spring solution insofar as an elastic element is connected integrally to a rotary part and interacts with a contour of an integrally formed section on a grip part. In addition to having cost advantages, such a simplified configuration of the switch allows simplified assembly of the switch. Furthermore, the rotary part is connected to the cable drum which can wind up a traction cable, which produces the connection to the gear of the bicycle, by virtue of rotation on the grip part.
The elastic element is preferably a spiral spring with a free resilient end which is of concavely curved configuration. The contour of the grip part engages in the concave curve of the spiral spring and pretensions the spiral spring when the grip part is rotated in the cable release direction. The contour slides on the free curve of the spiral spring when to grip part is rotated in the cable release direction such that the rotary part is displaced in an accelerated manner in the release direction of rotation once a disengagement means has disengaged the pawl and cleared the path for the rotary part to move to the next gear stage. In the switching direction in which the traction cable is tensioned, the rotary part is carried along directly by the grip part by the interaction of flanks to the next gear stage which is defined by the pawl latching into the latching toothing formation of the housing.
A functionally similar variant of an elastic element interacting with an integrally formed section is likewise a spiral spring with radially outwardly directed convex curvature and resilient end which is of bulbous configuration and butts under pretensioning against a socket of the integrally formed section on the grip part. When the grip part is actuated in the switching direction in which the traction cable is released, the convex curve of the spiral spring is bent, with a bulge being formed in the process, until the above-mentioned disengagement means releases the pawl for gear-changing purposes. The advantage of this solution is the interaction of the bulbous resilient end with the socket on the integrally formed section of the grip part. The socket may be configured such that a rolling movement, which is more or less free of friction, is produced there when the grip part is rotated in the switching direction in which the traction cable is released.
Finally, the invention proposes a further embodiment of an elastic element which, once again, is a spiral spring. In this embodiment, the spiral spring has at least one turn and an insertable resilient end which can be fastened in a rotatable, but form-fitting, manner in a receiving means of an integrally formed section on the grip part. It is advantageous here to use a plug-in connection, which can be inserted as early as during assembly of the switch. The advantage of this variant, in addition to the reliability of assembling the switch, resides in its low friction during actuation even under difficult lubrication conditions.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.